Alternating current rectifier of the selenium type



new June 19, 1945 v UNITED STATES PATENT orrics ALTERNATING CURRENT RECTIFIER 01" THE SELENIUM TYPE Leslie Ernest Thompson and Alexander Jenkins. London N. 1, England, assignors, by memo assignments, to f The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania No Drawing. Application January 8, 1048, Serial No. 471,738. In Great Britain January 21, I!

1 Claim. (Cl. 175-486) This invention relates to the manufacture of alternating current rectiiiers of the selenium type comprising a base or support provided with adirection and the so-called "bottom bend" characteristic, that is to say, the applied voltage in the forward direction at which eflective rectification takes place, the eiliciency of the rectifier in eommercialservice being dependent upon these characteristics. all of which vary within considerable limits in accordance with the-particular composition of the selenium mixture employed,

a the eventual resistance of the rectifier in thereverse direction being also determined by an electric forming process described for example in U. S. PatentNo. 2,270,187.

It is foimd-in practice that the resistance in the forward direction is favourably airected by the introduction oi relatively small quantities oi certain other substances into the selenium mixture and according to the present invention a relatively small amount of antimony is added to the selenium mixture described in United States Patent No. 2,307,474 for the purpose of reducing the iorward resistance of the rectifier.

The amount of added antimony for this purpose is found to be somewhat critical and is preferably of the order of 0.04%.

In a selenium composition prepared as de- 4 scribed for example in United BtatesjPatent No.

' proximately 22%.

2,307,474 the addition of 0.04% of antimony is round to reduce the forward resistance by ap- The improved process .of the invention is however not limited strictly to the valu'e given above by way of example which may be varied in accordance with the particular composition of the selenium mixture employed.

Having now described our inventiomfwhat we claim as new and desire to secure by Letters Patent is:

An alternating current rectifier comprising a base or support provided with a layer containing selenium, selenium dioxide. a halogen salt and approximately 0.04% of antimony.

LESLIE ERNEST THOMPSON. ALEXANDER JENKINS. 

